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LT8708 Dataheets PDF



Part Number LT8708
Manufacturers Linear
Logo Linear
Description 80V Synchronous 4-Switch Buck-Boost DC/DC Controller
Datasheet LT8708 DatasheetLT8708 Datasheet (PDF)

LT8708 80V Synchronous 4-Switch Buck-Boost DC/DC Controller with Bidirectional Capability FEATURES n Single Inductor Allows VIN Above, Below, or Equal to VOUT n Six Independent Forms of Regulation n VIN Current (Forward and Reverse) n VOUT Current (Forward and Reverse) n VIN and VOUT Voltage n Forward and Reverse Discontinuous Conduction Mode Supported n Supports MODE and DIR Pin Changes While Switching n VINCHIP Range 2.8V (Need EXTVCC > 6.4V) to 80V n VOUT Range: 1.3V to 80V n Synchronous Rec.

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LT8708 80V Synchronous 4-Switch Buck-Boost DC/DC Controller with Bidirectional Capability FEATURES n Single Inductor Allows VIN Above, Below, or Equal to VOUT n Six Independent Forms of Regulation n VIN Current (Forward and Reverse) n VOUT Current (Forward and Reverse) n VIN and VOUT Voltage n Forward and Reverse Discontinuous Conduction Mode Supported n Supports MODE and DIR Pin Changes While Switching n VINCHIP Range 2.8V (Need EXTVCC > 6.4V) to 80V n VOUT Range: 1.3V to 80V n Synchronous Rectification: Up to 99% Efficiency n Available in 40-Lead (5mm × 8mm) QFN with High Voltage Pin Spacing and 64-Lead (10mm × 10mm) eLQFP n AEC-Q100 Qualified for Automotive Applications APPLICATIONS n High Voltage Buck-Boost Converters n Bidirectional Charging System n Automotive 48V Systems DESCRIPTION The LT®8708 is a high performance buck-boost switching regulator controller that operates from an input voltage that can be above, below or equal to the output voltage. Features are included to simplify bidirectional power conversion in battery/capacitor backup systems and other applications that may need regulation of VOUT, VIN, IOUT, and/or IIN. Forward and reverse current can be monitored and limited for the input and output sides of the converter. All four current limits (forward input, reverse input, forward output and reverse output) can be set independently using four resistors on the PCB. The MODE pin can select between discontinuous conduction mode (DCM), continuous conduction mode (CCM), hybrid conduction mode (HCM) and Burst Mode® operation. In combination with the DIR (direction) pin, the chip can be configured to process power only from VIN to VOUT or only from VOUT to VIN. With a wide 2.8V to 80V input and 1.3V to 80V output range, the LT8708 is compatible with most solar, automotive, telecom and battery-powered systems. All registered trademarks and trademarks are the property of their respective owners. TYPICAL APPLICATION 10V TO 16V BATTERY VBAT1 + + – POWER TRANSFER DECISION LOGIC RVS (0V) FWD (3V) LD033 12V Bidirectional Dual Battery System with FHCM and RHCM ILIM TO DIODE DB1 ILIM TO DIODE DB2 VBAT2 + + 10V TO 16V – BATTERY 100 TG1 BOOST1 SW1 BG1 CSP CSN CSNIN CSPIN VINCHIP SHDN FBIN VINHIMON DIR SWEN LDO33 RVSOFF MODE VC LT8708 RT GND BG2 SW2 BOOST2 TG2 CSPOUT CSNOUT EXTVCC VOUTLOMON FBOUT INTVCC GATEVCC IMON_OP IMON_ON ICN ICP IMON_INP IMON_INN SS SYNC CLKOUT 8708 TA01a 126kHz DB1 DB2 TO TO BOOST1 BOOST2 EFFICIENCY (%) 99 98 97 96 95 94 10 Efficiency VBAT2 = 13.5V IOUT = 15A 12 14 VBAT1 (V) 16 8708 TA01b Rev. C Document Feedback For more information www.analog.com 1 LT8708 TABLE OF CONTENTS Features...................................................... 1 Applications................................................. 1 Typical Application ......................................... 1 Description.................................................. 1 Absolute Maximum Ratings............................... 3 Pin Configuration........................................... 3 Order Information........................................... 4 Electrical Characteristics.................................. 4 Typical Performance Characteristics.................... 9 Pin Functions............................................... 13 Block Diagram.............................................. 15 Operation................................................... 16 Typographical Conventions...................................... 16 Start-Up................................................................... 16 Start-Up: SHDN Pin............................................. 16 Start-Up: SWEN Pin............................................. 16 Start-Up: Soft-Start of Switching Regulator........ 17 Control Overview..................................................... 17 Power Switch Control ............................................. 18 Switch Control: Buck Region (VIN >> VOUT)........ 19 Switch Control: Buck-Boost (VIN ≅ VOUT)........... 19 Switch Control: Boost Region (VIN << VOUT)....... 20 Switch Control: Soft-Start...................................20 Uni and Bidirectional Conduction.............................20 Bidirectional Conduction: CCM ........................... 21 Unidirectional Conduction: DCM.......................... 21 Unidirectional Conduction: HCM..........................22 Unidirectional Conduction: Burst Mode...............22 Error Amplifiers.......................................................22 VOUT Regulation and Sensing..................................23 VOUT: Regulation..................................................23 VOUT: Above Regulation.......................................23 VOUT: Below Regulation and Undervoltage..........23 VIN Regulation and Sensing..................................... 24 VIN: Regulation.................................................... 24 VIN: Above Regulation and Overvoltage............... 24 VIN: Below Regulation......................


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